This invention relates to bulk material handling devices and, more particularly, to a rotatable wheel for reclaiming loose materials.
Coal, Ores, grains and other bulk materials are often stored in large, open piles. Such materials are sometimes also similarly heaped in the holds of ships or barges for transportation. In the past, material has been reclaimed from such piles by devices employing a series of buckets or scoops, mounted on a moving wheel or endless belt or chains, which dig material from the top or side of a pile, elevate the material to a point at or near the highest point of the path of motion and then discharge the material onto a moving conveyor belt or similar devices. Since the buckets or scoops often operate at the end of a boom, their weight is a major factor limiting the size and capacity of such devices.
In conventional bucket wheels, the material is discharged from the buckets or scoops by allowing it to fall by the force of gravity. The speed of such devices is limited by the time it takes to empty each bucket or scoop. At higher speeds, in addition to each bucket or scoop spending less time at the discharge position, increased centrifugal force tends to counteract gravity and actually slows the discharge of material.
Devices such as that described in U.S. Pat. No. 3,731,408 have been designed to operate at higher speeds by opening the scoops or buckets at the discharge point, thus allowing material to be discharged by the action of centrifugal force. Such devices have the disadvantage of requiring hinges, latches and other elements in the bucket or scoop that increase the weight and constitute points of wear and potential failure.
U.S. Pat. No. 3,357,118 describes a centrifugal discharge wheel excavator for open pit mining which employs open sided buckets. Those buckets utilize rubbing contact between the excavated material and the cut face to confine the material until it is lifted above the level of the face. After the material is lifted above the level of the face it is held in the bucket by a series of stationary retaining plates. Such a device is not well adapted to reclaiming loose material because the continual rubbing of the material against itself and the stationary plates causes increased power consumption and material degradation, and because the necessarily large clearances result in excessive leakage. In addition, irregularities in the top level of the stored material make it difficult to position the stationary retaining plates accurately.
Other centrifugal discharge designs have the buckets attached to a flexible member such as a chain or belt. These devices are designed to scoop up material as the buckets travel over a large diameter pulley which lessens centrifugal effects, elevate the buckets linearly which creates no centrifugal effect, and discharge the material as the buckets travel around a smaller diameter pulley which causes the centrifugal effect to be maximized. This design has several disadvantages: additional complexity involving many more moving parts than scoops that travel in a circular path; buckets which must be designed for both scooping material and discharging material through the same opening, thus disallowing optimal configuration for either action; and limitations in size and speed based on the relative diameters of the two pulleys.